1. Field of the Invention
The present invention relates to the manufacture of sports shoes comprising at least one portion projecting to the exterior of the shaft and/or of the sole and to shoes comprising such a projecting portion.
2. Discussion of Prior Art
Shoes provided with portions (or appendices) which project are known, such as athletic shoes provided with spikes under the sole, shoes for mountain climbing whose ends are equipped with spikes or spurs, shoes for use in competitive cycling comprising supports, ski boots, and particularly boots for use in mountainer skiing and cross-country skiing, etc.
In general, the projecting portions or appendices are attached to the lower or walking sole and as a result of this positioning, certain disadvantages result, both with respect to the comfort of the wearer and particularly with respect to the shoe itself. In effect, in these types of known shoes, the walking sole is subjected directly to intense mechanical effects (shear, traction, flexion), particularly in the linking regions between the sole and the projecting portions or appendices. These forces, with time, may possibly result in the deterioration of the sole and cause the separation of the sole from the projecting portions or appendices.
What has been noted above applies for all sports shoes of this type and more particularly for sports shoes used in cross-country or touring skiing, which are presently available on the market. These known cross-country ski boots are generally provided with a flexible walking sole comprising an extension on its front which is adapted to cooperate with the cross-country ski binding. This extension, which serves as a flexible blade, must allow for good movement of the foot during cross-country skiing. Yet, this solution suffers from certain disadvantages which relate to the operation of this flexible blade which is connected to the binding by a sort of pincer resting on the blade along a surface transverse to the longitudinal axis of the sole. As a result, the flexion blade used in this manner does not allow for optimum advancement of the foot, because, the frictional axis constituted by the surface of the squeezing pincer is situated too far ahead of the foot and thus increases the radius of movement as the foot is raised. Furthermore, the sole of this type of boot is subjected to mechanical forces essentially in the zone of the extension forming the flexion blade which, inter alia, necessitates the use of a sole material which is particularly resistant to fatigue and which exhibits good mechanical characteristics. Such soles are expensive and are nevertheless subject to deterioration.
French Pat. No. 2,345,181 (77 08705) discloses a ski boot comprising a sole made essentially out of rubber or other synthetic material. A metal armature 7 is arranged within the cross section of the sole. The armature extends from the heel of the boot up to the front of the projection portion.